Effect of low dosage of coagulant on the ultrafiltration membrane performance in feedwater treatment

Abstract

Low dosageCritical dose Ultrafiltration Flux decline a b s t r a c t One of the critical issues for the widely application of ultrafiltration (UF) in water treatment is membrane fouling owning to the dissolved organic matter. The aim of the present study is to explore the effect of various particle sizes caused by low dosages of coagulant with dissolved organic matter on the UF membrane performance. Aluminum chloride was added to the synthetic water with the hydrophobic humic acid (HA), the hydrophilic bovine serum albumin (BSA) e a protein-and their 1:1 (mass ratio) mixture. The results showed that there was a critical dose of Al that could cause dramatic flux reduction by blocking the membrane pores after coagulating with HA/BSA. For HA or BSA, the critical dose of Al was relatively lower at pH 6.0 than that at pH 8.0. After coagulation, the flux decline caused by HA was slightly varied as a function of pH while that caused by BSA was greatly affected by pH. The flux decline caused by the 1:1 (mass ratio) HA/BSA mixture after coagulation was similar to that caused by HA after coagulation because BSA could be encapsulated by HA. In addition, the peak value of the molecular weight (MW) distribution of HA coagulated with Al was changed more drastically compared to that of BSA after filtration. ª

Modification of ultrafiltration membrane with nanoscale zerovalent iron layers for humic acid fouling reduction

“…5b and c. Both the membrane flux and the corresponding HA removal efficiency were improved with increasing the ratio of ethanol (V ethanol /V solution ). This was due to more adsorption sites of NZVI particles and the smaller pore size of the NZVI layer, especially for those large MW HA molecules (80 ± 30 nm, Ma et al, 2014). It showed that membrane flux was significantly improved (final J/J 0 ¼ 0.62) in the presence of 75% ethanol compared to that in the absence of ethanol (final J/J 0 ¼ 0.45).…”

Influence of flocs breakage process on membrane fouling in coagulation/ultrafiltration process—Effect of additional coagulant of poly-aluminum chloride and polyacrylamide

“…Where coagulation/flocculation pre-treatment is used, the characteristics of the flocs will in-turn determine the structure of cake layer, and thus the efficiency of filtration [19,20]. Coagulation conditions, such as coagulant type and dose, [21,22] water quality, mixing mode [23,24], etc., have a great impact on characteristics of flocs.…”

Effect of aluminum speciation on ultrafiltration membrane fouling by low dose aluminum coagulation with bovine serum albumin (BSA)

“…A potential reason was that the particle size of BSA after coagulation steadily increased with increasing dose of alum salt. When BSA was coagulated with 7.5 mM alum salt, the particle size distribution was relatively close to the average membrane pore size, resulting in more chances of pore blocking and severe membrane fouling [29].…”

“…Our previous study has found that a low dose (critical dose) alum salt could accelerate membrane fouling after coagulating with protein [29]. More studies have shown that protein could cause serious UF membrane flux decline and many attempts have been used to control the fouling thus induced [30][31][32][33].…”